[Chinese expert consensus on the application of flow cytometry for the detectin of circulating plasma cells in plasma cell disorders (2024)].

Flow cytometry plays an important role in the diagnosis and treatment of plasma cell diseases, particularly in the detection of circulating plasma cells (CPCs) in the peripheral blood. A consensus about the normalized use of flow cytometry in detection of CPCs in peripheral blood in clinical practice has been achieved. This consensus is founded on evidence-based principles, which elucidates the timing and value of flow cytometry for the detection of CPCs in the monoclonal gammopathy of undetermined significance, smoldering myeloma, multiple myeloma, and plasma cell leukemia and standardizes flow cytometry in the detection of CPCs in plasma cell diseases.

Circulating plasma cells as a predictive biomarker in Multiple myeloma: an updated systematic review and meta-analysis.

BACKGROUND: Circulating plasma cells (CPCs) are defined by the presence of peripheral blood clonal plasma cells, which would contribute to the progression and dissemination of multiple myeloma (MM). An increasing number of studies have demonstrated the predictive potential of CPCs in the past few years. Therefore, there is a growing need for an updated meta-analysis to identify the specific relationship between CPCs and the prognosis of MM based on the current research status. METHODS: The PubMed, Embase, and Cochrane Library databases were screened to determine eligible studies from inception to November 5, 2023. Publications that reported the prognostic value of CPCs in MM patients were included. Hazard ratios (HRs) with 95% confidence intervals (CIs) of overall survival (OS) and progression-free survival (PFS) were extracted to pool the results. Subgroup analyses were performed based on region, sample size, cut-off value, detection time, initial treatment, and data type. The association between CPCs level and clinicopathological characteristics, including the International Staging System (ISS), Revised-ISS (R-ISS), and cytogenetic abnormalities were also evaluated. Statistical analyses were conducted using STATA 17.0 software. RESULTS: Twenty-two studies with a total of 5637 myeloma patients were enrolled in the current meta-analysis. The results indicated that myeloma patients with elevated CPCs were expected to have a poor OS (HR = 2.19, 95% CI: 1.81-2.66, p < 0.001) and PFS (HR = 2.45, 95% CI: 1.93-3.12, p < 0.001). Subgroup analyses did not alter the prognostic role of CPCs, regardless of region, sample size, cut-off value, detection time, initial treatment, or data type. Moreover, the increased CPCs were significantly related to advanced tumour stage (ISS III vs. ISS I-II: pooled OR = 2.89, 95% CI: 2.41-3.46, p < 0.001; R-ISS III vs. R-ISS I-II: pooled OR = 3.65, 95% CI: 2.43-5.50, p < 0.001) and high-risk cytogenetics (high-risk vs. standard-risk: OR = 2.22, 95% CI: 1.60-3.08, p < 0.001). CONCLUSION: Our meta-analysis confirmed that the increased number of CPCs had a negative impact on the PFS and OS of MM patients. Therefore, CPCs could be a promising prognostic biomarker that helps with risk stratification and disease monitoring.

There is a growing need for an updated meta-analysis to identify the specific relationship between CPCs and the prognosis of MM based on the current research status.Our meta-analysis revealed that a high CPCs level was significantly associated with worse OS and PFS in MM patients.CPCs could be a promising predictive biomarker that helps with risk stratification and disease monitoring.

Prognostic Implications of Circulating Plasma Cell Percentage in Multiple Myeloma and Primary Plasma Cell Leukemia Defined by New Criteria.

INTRODUCTION: The definition of primary plasma cell leukemia (pPCL) has been revised from ≥20% to ≥5% circulating plasma cells (CPC). However, the precise prognosis associated with CPC remains controversial. This study aimed to investigate prognostic biomarkers for myeloma patients based on CPC presence. METHODS: A comprehensive analysis was conducted on 309 consecutive patients diagnosed with either multiple myeloma or pPCL, utilizing peripheral blood smears stained with Wright-Giemsa. RESULTS: Patients were grouped by CPC percentage: 0% (221, 71.5%), 1-4% (49, 15.9%), 5-19% (16, 5.2%), ≥20% (23, 7.4%). CPC >5% correlated with unfavorable characteristics, including anemia, renal dysfunction, and advanced International Staging System. Common cytogenetic abnormalities such as 1q21 amplification, 17p deletion, and Myc rearrangement were prevalent among CPC-positive patients. Median progression-free survival (PFS) and overall survival (OS) were shorter in patients with CPC ≥5% (29.47 vs. 10.03 months; 64.10 vs. 12.30 months). Additionally, PFS and OS were shorter in CPC-positive patients without autologous hematopoietic stem cell transplantation (ASCT) and those with response < partial remission to the first-line regimen. Furthermore, an association emerged between soft tissue-related extramedullary disease and inferior PFS, while Myc rearrangement correlated with abbreviated OS. CONCLUSION: Biological characteristics displayed greater aggressiveness in patients with positive CPC, leading to significantly shorter PFS and OS. The presence of CPC, ASCT, and overall response rate were independent prognostic factors. While no new threshold for pPCL with CPCs is proposed, Myc rearrangements and CPC positivity could serve as ultra-high-risk factors for multiple myeloma.

Early Detection and Diagnostic Approach Through Automated Hematological Analysis for Plasma Cell Leukemia.

Plasma cell leukemia (PCL) is a clinically aggressive variant of multiple myeloma, characterized by a high burden of circulating plasma cells, necessitating swift and accurate diagnosis due to its poor prognosis. The conventional diagnostic criteria, including the recent recommendation by the International Myeloma Working Group (IMWG) of > 5% circulating plasma cells as positive, have evolved over time. In this context, we present a detailed case report that underscores the pivotal role of the ADVIA 2120 automated hematology counter in detecting plasma cells through cytogram analysis, along with the significance of routine peripheral blood smear analysis and the utility of a large unstained cells (LUCs) threshold of > 4.5% as an indicator for PCL. The case involves a 64-year-old patient with relapsed multiple myeloma and stable paraprotein levels who experienced sudden renal impairment. In this case report, we highlight how ADVIA analysis and cytochemistry assisted in the diagnosis, and further explore ADVIA's utility in this challenging leukemia.

Imaging flow cytometric detection of del(17p) in bone marrow and circulating plasma cells in multiple myeloma.

BACKGROUND: Detection of del(17p) in myeloma is generally performed by fluorescence in situ hybridization (FISH) on a slide with analysis of up to 200 nuclei. The small cell sample analyzed makes this a low precision test. We report the utility of an automated FISH method, called "immuno-flowFISH", to detect plasma cells with adverse prognostic risk del(17p) in bone marrow and blood samples of patients with myeloma. METHODS: Bone marrow (n = 31) and blood (n = 19) samples from 35 patients with myeloma were analyzed using immuno-flowFISH. Plasma cells were identified by CD38/CD138-immunophenotypic gating and assessed for the 17p locus and centromere of chromosome 17. Cells were acquired on an AMNIS ImageStreamX MkII imaging flow cytometer using INSPIRE software. RESULTS: Chromosome 17 abnormalities were identified in CD38/CD138-positive cells in bone marrow (6/31) and blood (4/19) samples when the percent plasma cell burden ranged from 0.03% to 100% of cells. Abnormalities could be identified in 14.5%-100% of plasma cells. CONCLUSIONS: The "immuno-flowFISH" imaging flow cytometric method could detect del(17p) in plasma cells in both bone marrow and blood samples of myeloma patients. This method was also able to detect gains and losses of chromosome 17, which are also of prognostic significance. The lowest levels of 0.009% (bone marrow) and 0.001% (blood) for chromosome 17 abnormalities was below the detection limit of current FISH method. This method offers potential as a new means of identifying these prognostically important chromosomal defects, even when only rare cells are present and for serial disease monitoring.

Detection of circulating plasma cells in peripheral blood using deep learning-based morphological analysis.

BACKGROUND: The presence of circulating plasma cells (CPCs) is an important laboratory indicator for the diagnosis, staging, risk stratification, and progression monitoring of multiple myeloma (MM). Early detection of CPCs in the peripheral blood (PB) followed by timely interventions can significantly improve MM prognosis and delay its progression. Although the conventional cell morphology examination remains the predominant method for CPC detection because of accessibility, its sensitivity and reproducibility are limited by technician expertise and cell quantity constraints. This study aims to develop an artificial intelligence (AI)-based automated system for a more sensitive and efficient CPC morphology detection. METHODS: A total of 137 bone marrow smears and 72 PB smears from patients with at Zhongshan Hospital, Fudan University, were retrospectively reviewed. Using an AI-powered digital pathology platform, Morphogo, 305,019 cell images were collected for training. Morphogo's efficacy in CPC detection was evaluated with additional 184 PB smears (94 from patients with MM and 90 from those with other hematological malignancies) and compared with manual microscopy. RESULTS: Morphogo achieved 99.64% accuracy, 89.03% sensitivity, and 99.68% specificity in classifying CPCs. At a 0.60 threshold, Morphogo achieved a sensitivity of 96.15%, which was approximately twice that of manual microscopy, with a specificity of 78.03%. Patients with CPCs detected by AI scanning had a significantly shorter median progression-free survival compared with those without CPC detection (18 months vs. 34 months, p< .01). CONCLUSIONS: Morphogo is a highly sensitive system for the automated detection of CPCs, with potential applications in initial screening, prognosis prediction, and posttreatment monitoring for MM patients. PLAIN LANGUAGE SUMMARY: Diagnosing and monitoring multiple myeloma (MM), a type of blood cancer, requires identifying and quantifying specific cells called circulating plasma cells (CPCs) in the blood. The conventional method for detecting CPCs is manual microscopic examination, which is time-consuming and lacks sensitivity. This study introduces a highly sensitive CPC detection method using an artificial intelligence-based system, Morphogo. It demonstrated remarkable sensitivity and accuracy, surpassing conventional microscopy. This advanced approach suggests that early and accurate CPC detection is achievable by morphology examination, making efficient CPC screening more accessible for patients with MM. This innovative system has the potential to be used in the diagnosis and risk assessment of MM.

Multiparametric Flow Cytometry in the Evaluation of Plasma Cell Proliferative Disorders: Current Paradigms for Clinical Practice.

Diagnosis of plasma cell proliferative disorders (PCPDs) is primarily based on the demonstration of monoclonal protein (M-Protein) in blood and/ or urine which often precedes clinical manifestations of the disease. The basic pathophysiology behind the M-protein presence is the proliferation of clonal plasma cells (PCs) in bone marrow or extramedullary sites and is assessed using cytomorphology and immunophenotyping. The role of multiparametric flow cytometry (MFC) for PC identification is technically the most valuable tool in this context as it characterizes as well as quantifies the clonal PCs based on differential expression of various immunophenotypic (IPT) markers. From a diagnostic perspective, MFC is critical in the definite identification of the clonal PCs and delineates benign and borderline entities at one end of the spectrum (MGUS, SMM) with lower clonal PC% and, malignant diseases at the other end (MM and PCL) with higher clonal PC fraction. The role of MFC in assessment of measurable residual disease (MRD) and monitoring of progression in MM and various PCPDs has been validated in multiple clinical studies and is probably one of the most promising tools for predicting treatment outcomes. Furthermore, MFC also plays a crucial role in disease prognostication based on specific IPT profiles. An additional role of MFC in the current clinical scenario is the evaluation of tumor microenvironment based on immune cell repertoire, which is reflecting encouraging results across. Thus, in the current review we concisely describe the role of MFC as a reliable and essential modality in PCPDs, from diagnosis to prediction of treatment outcome and disease monitoring.

Plasma Cell Leukemia-Clinicopathological Profile from a Tertiary Care Center in Western India.

Poornima ManimaranIntroduction Plasma cell leukemia (PCL) is very uncommon and aggressive neoplasm constituting 2 to 4% of all plasma cell dyscrasias. By definition, clonal plasma cells should make up 20% of peripheral blood or have an absolute plasma cell count of 2 × 10 9 cells/cu.mm. PCL can be primary or secondary. In this study, the clinicohematological features of PCL, and correlation of immunophenotypic profile and conventional therapies with overall survival was analyzed. Materials and Methods This retrospective study involved PCL patients who were diagnosed across a 12-year period, from 2010 to 2021, at a tertiary care center in western India. Clinical, biochemical, peripheral smear, bone marrow aspirate, immunophenotyping, and molecular analysis were performed. Results Total 39 PCL patients were included in the study among which 36 were primary PCL patients. Splenomegaly (10/27), hepatomegaly (6/26), and lymphadenopathy (5/23) were noted. At presentation, all patients had anemia (<11g/dL), thrombocytopenia (33/39), hypercalcemia (>11mg/dl) 10/33 (30.3%) and lytic lesions was noted in 18/26 (69.2%). Immunophenotype of these patients showed CD 38 positivity, CD 138 positivity, CD56 positivity, and CD 117 negativity were 100, 62, 41.6, and 89%, respectively. Overall survival of our patients was 4.1 months and overall survival of patients treated with VTD (bortezomib, thalidomide, dexamethasone) and VCD (bortezomib, cyclophosphamide, dexamethasone) regimen was 3.4 and 4.1 months, respectively, which was not statically significant ( p -value 0.816). CD117 and CD56 markers were also not having any prognostic significance ( p -value 1.000 and 0.873, respectively). Conclusion Because of rarity of the disease, prospective studies are very limited and hence management and outcome of the disease are difficult to analyze. The current treatment protocols have no survival advantage and hence newer therapeutic approach is mandatory to attain better outcome.

[Effect of Circulating Plasma Cells on the Prognosis of Patients with Multiple Myeloma].

OBJECTIVE: to analyze the effect of circulating plasma cells(CPC) on the prognosis of patients with multiple myeloma(MM) in the era of new drugs, and to explore the new definition standard of primary plasma cell leukemia(pPCL). METHODS: The clinical data of 321 patients with newly diagnosed MM and 21 patients with pPCL admitted to our hospital from January 2014 to May 2022 were retrospectively analyzed. According to the proportion of CPC in peripheral blood smears, all patients were divided into 4 groups: CPC 0% group(211 cases), CPC 1%-4% group(69 cases), CPC 5%-19% group(41 cases) and CPC≥20% group(21 cases). The clinical features of patients in each group were compared and the prognosis fators was analyzed. RESULTS: The median OS of the four groups were 44.5,21.3,24.6 and 12.8 months, respectively. Among them, 295 patients(86.3%) were treated with new drugs, and the median OS of the four groups were not reached, 26.7, 24.6 and 14.9 months, respectively. As the survival curves of CPC 5%-19% group and CPC≥20% group were similar, the patients were divided into CPC<5% group and CPC≥5% group, the median OS of CPC<5% group was better than that in CPC≥5% (43.5 vs 22.3 months, P<0.001). In addition, the median OS of patients in the CPC 1%-4% group was also significantly lower than that in the CPC 0% group and similar to that in the CPC≥5% group. Multivariate analysis showed that 1%-4% CPC was an independent risk factor for the OS of patients with CPC<5%. The patients with CPC<5% were stratified by R-ISS staging, and the OS of R-ISS stage Ⅰ or stage Ⅱ with 1%-4% CPC was similar to that of R-ISS stage Ⅲ. The newly defined pPCL patients showed increased tumor load and obvious invasive characteristics. Multivariate analysis showed no independent prognostic factors for pPCL, and high-risk cytogenetic abnormalities(HRCA) had no significant effect on the prognosis. CONCLUSION: The validity of IMWG's new pPCL definition standard was verified, and it was found that the survival of MM with 1%-4% CPC also is poor and the prognosis is very close to pPCL. In addition, the newly defined pPCL has unique clinical and biological characteristics.

The prognostic significance of circulating plasma cells in newly diagnosed multiple myeloma patients.

Objective: Multiple myeloma (MM) is a highly characteristic tumor that is influenced by numerous factors that determine its prognosis. Studies indicate that the presence of circulating plasma cells (cPCs) is a detrimental factor that significantly impacts the prognosis of patients with MM. Methods: This study retrospectively analyzed the prognostic value of cPCs quantified by 10-color flow cytometry in 145 newly diagnosed MM (NDMM) cases in the First Affiliated Hospital of Soochow University from November 2018 to February 2021. The study was approved by the Ethics Committee of the hospital (2021 No. 93). Results: Of the 145 patients, 99 (68.2%) were detected cPCs. Through receiver operating characteristics (ROC) analysis, an optimal threshold of 0.165% was identified as a predictor for overall survival (OS). The median progression-free survival (PFS) was 33 months in patients with cPCs ≥0.165%, whereas those with cPCs <0.165% had a PFS of <33 months (p=0.001). The median OS was not reached for two groups; the 3-year OS for patients with cPCs ≥0.165% was 71% compared with 87% for those with cPCs <0.165% (p=0.003). In transplant patients, cPCs ≥0.165% also predicted worse prognosis. Similarly, when considering cytogenetic risk factors in conjunction with cPC levels, comparable results were obtained. To evaluate whether the Revised International Staging System (R-ISS) groups could be further stratified based on different prognostic factors related to cPCs, our study revealed similar median PFS and OS rates in R-ISS II stage patients with cPCs ≥0.165% compared to those in the III stage (p=0.659 and 0.249, respectively). Conclusion: This study demonstrates that a high ratio of cPCs serves as a reliable indicator for predicting a poorer prognosis in MM cases. Furthermore, incorporating the R-ISS system and cytogenetic risk factors alongside the level of cPCs enhances the accuracy of prognostic predictions for patients with MM.

High-risk multiple myeloma predicted by circulating plasma cells and its genetic characteristics.

Introduction: Circulating plasma cells (CPC) have been reported to be one of the indicators of high-risk multiple myeloma (MM), yet the prognostic significance of CPC in Chinese population and the genetic mechanisms underlying CPC formation have not been fully elucidated. Methods: Patients with newly diagnosed MM were included in this study. We used multi-parameter flow cytometry (MFC) for CPC quantification and next-generation sequencing (NGS) technology for mutational landscape mapping to identify the correlation of CPC level with clinical characteristics and the mutations. Results: A total of 301 patients were enrolled in this investigation. We demonstrated that CPC quantification could effectively mirror the tumor load, and CPC ≥ 0.105% at diagnosis or detectable CPC after therapy indicates poor treatment response and adverse outcome, and the introduction of CPC into the R-ISS enables a more accurate risk stratification. Interestingly, we noticed an elevated percentage of light-chain MM in patients with higher CPC. Mutational landscape revealed that patients harboring mutations in TP53, BRAF, DNMT3A, TENT5C, and IL-6/JAK/STAT3 pathway-related genes tended to have higher CPC levels. Gene enrichment analysis demonstrated that pathways involving chromosome regulation and adhesion may be potential mechanisms accounting for CPC formation. Discussion: Accordingly, quantification of CPC may provide a less-invasive and reliable approach for identifying high-risk MM in Chinese population.

Characterization of BCMA Expression in Circulating Rare Single Cells of Patients with Plasma Cell Neoplasms.

B-cell maturation antigen (BCMA), a key regulator of B-cell proliferation and survival, is highly expressed in almost all cases of plasma cell neoplasms and B-lymphoproliferative malignancies. BCMA is a robust biomarker of plasma cells and a therapeutic target with substantial clinical significance. However, the expression of BCMA in circulating tumor cells of patients with hematological malignancies has not been validated for the detection of circulating plasma and B cells. The application of BCMA as a biomarker in single-cell detection and profiling of circulating tumor cells in patients' blood could enable early disease profiling and therapy response monitoring. Here, we report the development and validation of a slide-based immunofluorescence assay (i.e., CD138, BCMA, CD45, DAPI) for enrichment-free detection, quantification, and morphogenomic characterization of BCMA-expressing cells in patients (N = 9) with plasma cell neoplasms. Varying morphological subtypes of circulating BCMA-expressing cells were detected across the CD138(+/-) and CD45(+/-) compartments, representing candidate clonotypic post-germinal center B cells, plasmablasts, and both normal and malignant plasma cells. Genomic analysis by single-cell sequencing and correlation to clinical FISH cytogenetics provides validation, with data showing that patients across the different neoplastic states carry both normal and altered BCMA-expressing cells. Furthermore, altered cells harbor cytogenetic events detected by clinical FISH. The reported enrichment-free liquid biopsy approach has potential applications as a single-cell methodology for the early detection of BCMA+ B-lymphoid malignancies and in monitoring therapy response for patients undergoing anti-BCMA treatments.

[Clinical Characteristics of Multiple Myeloma Patients with Early Relapse].

OBJECTIVE: To analyze the clinical characteristics of multiple myeloma(MM) patients with early relapse. METHODS: A total of 50 MM patients with early relapse (≤12 months) and 50 matched controls with late relapse (>12 months) were selected. The time from diagnosis to relapse and related clinical data of the 100 patients were retrospectively analyzed, and the factors associated with early relapse were identified. Kaplan-Meier curve was used to analyze the overall survival (OS) time of the whole cohort. Area under the curve (AUC) was used to evaluate the effect of circulating plasma cells on early recurrence of the patients. RESULTS: The results showed that high-risk cytogenetics (FISH) (P=0.005), and ISS stage III (P=0.008) were associated with early recurrence of the patients. For patients with early relapse, high-risk FISH showed poor survival. Compared with the patients with late relapse, most of the chromosome karyotype of patients with early relapse showed quantitative and structural abnormalities. The expression of circulating plasma cells was significantly increased in patients with early recurrence group (P=0.0318). The response to initial treatment was poor in the early recurrence group (P=0.001), and the prognosis was significantly worse than those in the late recurrence group (median OS: 38 vs 81 months, P=0.002). CONCLUSION: Early relapse is a marker poor prognostic in MM patients, and such patients should be focused on the improving their prognosis.

Enrichment-Free Single-Cell Detection and Morphogenomic Profiling of Myeloma Patient Samples to Delineate Circulating Rare Plasma Cell Clones.

Multiple myeloma is an incurable malignancy that initiates from a bone marrow resident clonal plasma cell and acquires successive mutational changes and genomic alterations, eventually resulting in tumor burden accumulation and end-organ damage. It has been recently recognized that myeloma secondary genomic events result in extensive sub-clonal heterogeneity both in localized bone marrow areas and circulating peripheral blood plasma cells. Rare genomic subclones, including myeloma initiating cells, could be the drivers of disease progression and recurrence. Additionally, evaluation of rare myeloma cells in blood for disease monitoring has numerous advantages over invasive bone marrow biopsies. To this end, an unbiased method for detecting rare cells and delineating their genomic makeup enables disease detection and monitoring in conditions with low abundant cancer cells. In this study, we applied an enrichment-free four-plex (CD138, CD56, CD45, DAPI) immunofluorescence assay and single-cell DNA sequencing for morphogenomic characterization of plasma cells to detect and delineate common and rare plasma cells and discriminate between normal and malignant plasma cells in paired blood and bone marrow aspirates from five patients with newly diagnosed myeloma (N = 4) and monoclonal gammopathy of undetermined significance (n = 1). Morphological analysis confirms CD138+CD56+ cells in the peripheral blood carry genomic alterations that are clonally identical to those in the bone marrow. A subset of altered CD138+CD56- cells are also found in the peripheral blood consistent with the known variability in CD56 expression as a marker of plasma cell malignancy. Bone marrow tumor clinical cytogenetics is highly correlated with the single-cell copy number alterations of the liquid biopsy rare cells. A subset of rare cells harbors genetic alterations not detected by standard clinical diagnostic methods of random localized bone marrow biopsies. This enrichment-free morphogenomic approach detects and characterizes rare cell populations derived from the liquid biopsies that are consistent with clinical diagnosis and have the potential to extend our understanding of subclonality at the single-cell level in this disease. Assay validation in larger patient cohorts has the potential to offer liquid biopsy for disease monitoring with similar or improved disease detection as traditional blind bone marrow biopsies.

The Cytogenetic Profile of Primary and Secondary Plasma Cell Leukemia: Etiopathogenetic Perspectives, Prognostic Impact and Clinical Relevance to Newly Diagnosed Multiple Myeloma with Differential Circulating Clonal Plasma Cells.

Plasma cell leukemia (PCL) is a rare and aggressive plasma cell dyscrasia that may appear as de-novo leukemia (pPCL) or on the basis of a pre-existing multiple myeloma (MM), called secondary plasma cell leukemia (sPCL). In this prospective study, we have applied a broad panel of FISH probes in 965 newly diagnosed MM (NDMM) and 44 PCL cases of both types to reveal the particular cytogenetic differences among the three plasma cell dyscrasias. In order to evaluate the frequency and patterns of clonal evolution, the same FISH panel was applied both at diagnosis and at the time of first relapse for 81 relapsed MM patients and both at MM diagnosis and during sPCL transformation for the 19 sPCL cases described here. pPCL was characterized by frequent MYC translocations and t(11;14) with a 11q13 breakpoint centered on the MYEOV gene, not commonly seen in MM. sPCL had a higher number of FISH abnormalities and was strongly associated with the presence of del(17p13), either acquired at the initial MM stage or as a newly acquired lesion upon leukemogenesis in the context of the apparent clonal evolution observed in sPCL. In clinical terms, sPCL showed a shorter overall survival than pPCL with either standard or high-risk (t(4;14) and/or t(14;16) and/or del(17p13) and/or ≥3 concomitant aberrations) abnormalities (median 5 months vs. 21 and 11 months respectively, p < 0.001), suggesting a prognostic stratification based on cytogenetic background. These observations proved relevant in the NDMM setting, where higher levels of circulating plasma cells (CPCs) were strongly associated with high-risk cytogenetics (median frequency of CPCs: 0.11% of peripheral blood nucleated cells for high-risk vs. 0.007% for standard-risk NDMM, p < 0.0001). Most importantly, the combined evaluation of CPCs (higher or lower than a cut-off of 0.03%), together with patients' cytogenetic status, could be used for an improved prognostic stratification of NDMM patients.

Monitoring multiple myeloma in the peripheral blood based on cell-free DNA and circulating plasma cells.

With the advent of novel, highly effective therapies for multiple myeloma (MM), classical serologic monitoring appears insufficient for response assessment and prediction of relapse. Moreover, serologic studies in MM are hampered by interference of therapeutic antibodies. The detection of malignant plasma cell clones by next generation sequencing (NGS) or multiparameter flow cytometry (MFC) circumvents these difficulties and can be performed in the peripheral blood (pB) by targeting circulating cell-free DNA (cfDNA) or circulating plasma cells (CPCs), thus also avoiding an invasive sampling procedure. Here, we applied NGS of VJ light chain (LC) rearrangements in cfDNA and MFC of magnetically-enriched CD138-positive CPCs (me-MFC) to investigate disease burden in unselected MM patients. Sequencing was successful for 114/130 (87.7%) cfDNA samples and me-MFC results were analyzable for 196/205 (95.6%) samples. MM clones were detectable in 38.9% of samples taken at initial diagnosis or relapse (ID/RD), but only in 11.8% of samples taken during complete remission (CR). Circulating MM plasma cells were present in 83.3% of ID/RD samples and 9.9% of CR samples. Residual disease assessment by NGS or me-MFC in samples taken during very good partial remission or CR was 80% concordant. Notably, 4/4 (NGS) and 5/8 (me-MFC) positive CR samples were from patients with oligo- or non-secretory myeloma. The time to progression was shorter if there was evidence of residual myeloma in the pB. Together, our findings indicate that our two novel analytical approaches accurately indicate the course of MM and may be particularly valuable for monitoring patients with serologically non-trackable disease.

Plasma cell leukemia: A review of the molecular classification, diagnosis, and evidenced-based treatment.

Plasma cell leukemia is a rare and aggressive plasma cell dyscrasia associated with dismal outcomes. It may arise de novo, primary plasma cell leukemia, or evolve from an antecedent diagnosis of multiple myeloma, secondary plasma cell leukemia. Despite highly effective therapeutics, survival for plasma cell leukemia patients remains poor. Molecular knowledge of plasma cell leukemia has recently expanded with use of gene expression profiling and whole exome sequencing, lending new insights into prognosis and therapeutic development. In this review, we describe the molecular knowledge, clinical characteristics, evidenced-based therapeutic approaches and treatment outcomes of plasma cell leukemia.

Blood-based risk stratification for pre-malignant and symptomatic plasma cell neoplasms to improve patient management.

Standard risk stratification (sRisk) guides clinical management in monoclonal gammopathy of undetermined significance (MGUS), smoldering multiple myeloma (SMM) and multiple myeloma (MM). Nonetheless, clinical results are considerably heterogeneous among patients with similar risk status. Blood and bone marrow samples from 276 MGUS, 56 SMM and 242 MM in regular clinical practice were analyzed at diagnosis by flow cytometry. Higher levels of aberrant circulating plasma cells (cPC) (> 0.0035% of leukocytes), combined with albumin, beta2-microglobuline and lactate-dehydrogenase levels, offered minimally-invasive risk stratification (RcPC) with results comparable to sRisk. RcPC and sRisk 10-year progression-free-survival (10y-PFS) rates were: 93.8% vs. 95.1% for low-risk, 78.4% vs. 81.7% for intermediate-risk and 50.0% vs. 47.8% for high-risk MGUS; 58.3% vs. 57.8% low-risk, 44.4% vs. 45.8% intermediate-risk and 8.9% vs. 15.0% high-risk SMM; and 44.4% vs. 44.4% low-risk, 36.1% vs. 36.8% intermediate-risk, and 13.3% vs. 16.2% high-risk MM. Circulating-PC > 0.0035% vs. cPC<0.0035% was an independent prognostic factor for PFS (HR=4.389, P=1.2×10-15, Harrell C-statistic =0.7705±0.0190) and over-all survival (OS, HR=4.286, 2.3×10-9, Harrell C-statistic =0.8225±0.0197) that complemented sRisk in patients with low-sRisk (10y-PFS rates 48.1% vs. 87.3%, P=1.2×10-8) and intermediate-sRisk (10y-PFS rates 28.9% vs. 74.1%, P=8.6×10-12). Patients with high cPCs values are associated with higher proliferation and lower apoptosis rates of PC. Circulating-PC > 0.0035% identified MGUS, SMM and MM patients at higher risk of progression or death and predicted a cohort of patients that after relapse from stringent complete response showed shorter OS. These patients could benefit from early consolidation therapy, tandem ASCT or intensive maintenance.

Prognostic value of circulating clonal plasma cells in newly diagnosed multiple myeloma.

OBJECTIVES: Multiple myeloma (MM) involves a clinically and biologically heterogeneous malignancy of plasma cells. It is difficult to predict the prognosis of MM. The presence of circulating clonal plasma cells (CPC) has been associated with a worse prognosis in patients with MM. METHODS: This study retrospectively analysed CPC in 108 newly diagnosed MM patients by 8-colour flow cytometry to investigate their value for predicting the outcome and combined the level of CPC with the revised International Staging System (R-ISS) to stratify the MM patients according to risk. RESULTS: CPC were detected in 58/108 patients (53.7%). The optimum cut-off for the prediction of overall survival was determined to be 0.105%. Patients with higher R-ISS stages seemed to harbour more CPC. A level of CPC≥0.105% was an independent risk factor for adverse outcomes (P<0.001). The combination of the R-ISS staging system and level of CPC was used to stratify MM patients according to risk, and the combination of R-ISS stage III and a level of CPC≥0.105% defined the ultra-high-risk group. CONCLUSION: This study suggests that a high proportion of CPC is associated with aggressive disease and that the use of the current R-ISS system in conjunction with assessment of the level of CPC may facilitate the stratification of newly diagnosed MM patients into clinically relevant prognostic subgroups.

The detection of circulating plasma cells may improve the Revised International Staging System (R-ISS) risk stratification of patients with newly diagnosed multiple myeloma.

The Revised International Staging System (R-ISS) stratifies patients affected by Multiple Myeloma (MM) into three distinct risk groups: R-ISS I [ISS Stage I, Standard-Risk cytogenetics and normal Lactase DeHydrogenase (LDH)], R-ISS III (ISS stage III and either high-risk cytogenetics or high LDH) and R-ISS II (any other characteristics). With the aim to verify whether the three R-ISS groups could be divided into subgroups with different prognostic factors based on the detection of Circulating Plasma Cells (CPCs) at diagnosis, in this retrospective analysis, we evaluated 161 patients with MM treated at our centre between 2005 and 2017. In all, 57 patients (33·9%) were staged as R-ISS III, 98 (58·3%) as R-ISS II and six (3·6%) as R-ISS I. CPCs were detected in 125 patients (74·4%), while in 43 patients (25·6%) no CPCs were seen. Our analysis revealed that Overall Survival (OS) and progression-free survival (PFS) rates in R-ISS II patients were higher in the subgroup without CPCs compared to the subgroup with ≥1 CPCs (OS: 44·7% vs. 16·3%, P = 0·0089; PFS: 27·8% vs. 8·1%, P = 0·0118). Our present findings suggest that the detection of CPCs at diagnosis may be used as a further prognostic biomarker to improve the risk stratification of patients with MM staged as R-ISS II.